Hyaline Hyphomyces Forming Conidia in Clusters

Acremonium

Formerly known as Cephalosporium because of the resemblance of clusters
of conidia to the convolutions of a (admittedly tiny) brain

Often considered a contaminant; may cause mycetoma, corneal infection,
onychomycosis, and rarely other disease

Colonies have a smooth, yeast-like appearance and pastel color or may be
felt-like, folded, and compact, evolving to loose, white and cottony. The reverse
is colorless, pale yellow, or pink-gray

Extremely delicate, septate hyphae

Erect, unbranched, delicate phialides extend at right angles from hyphae

Conidia are oblong and may resemble clustered grains of rice

Conidia are easily disrupted; naked phialides and scattered conidia may
predominate, as in Figure 2 below

FIG. 1.Acremonium in slide culture. Note the
delicate hyphae indicated by the arrowhead and the phialide
indicated by the arrow.

FIG. 2.Acremonium. The frail connection between
phialide and conidia often makes it difficult to locate clustered
conidia at the tip of phialides.

Fusarium

Generally considered a contaminant, but may cause eye, skin, and systemic
infections, usually in immunocompromised people

Colonies
are fast-growing, variable in color and texture, often granular
or fluffy, rose-red, purple, or lavender; as with many molds, may start
as white, cottony colonies, darkening with maturity. The reverse is pale, but may darken with age

Trichoderma

Usually considered a contaminant; may cause disease in immunocompromised host

Colonies on Sabouraud. dextrose agar often are white and fluffy when young but are typically
green, granular, and poorly demarcated with maturity, growing across the entire
plate; this has been termed the "green lawn" appearance
(see also Gliocladium, below)

Phialides resemble those of Paecilomyces (bowling pin form) and extend in pairs
opposite of one another at 45° from the hyphae

Conidia appear singly or in clusters at the tip of the phialides in a somewhat
less organized pattern than Gliocladium, and are 3μ in diameter

FIG. 1.Trichoderma in slide culture.

Gliocladium

Usually considered a contaminant

Colonies on Sabouraud. dextrose agar are white initially, but typically become
green, granular, poorly demarcated, and grow across the
entire plate, resembling a "green lawn" (see also
Trichoderma, above)

Phialides branching and tapered at tips

Spherical conidia are gathered at tip of phialides in a tight, ball-shaped cluster
and are often somewhat larger than those of Trichoderma